0ccdf54b removed stack allocated THD objects from functions
Wsrep_schema::replay_transaction(). However, it inadvertedly
anticipated the destruction of the THD, causing assertions and usage
of THD after it was destroyed.
The fix consists in extracting the original function into a separate
function, and leave the allocation and destruction of the THD object
in Wsrep_schema::replay_transaction(), making sure that using the heap
allocated THD has no side effects.
Same for Wsrep_schema::recover_sr_transactions().
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>